The lubricating property is required for oils such as cutting oil, grinding oil, polishing oil, rolling oil, drawing oil, pressing oil, forging oil and metalworking oils used for working silicon wafers such as polishing and cutting. As the metalworking oil, in general, oils insoluble in water which are prepared by adding various additives to mineral oils or oils soluble in water which are prepared by adding various additives to mineral oils or synthetic oils and used after being diluted with water, are used. Heretofore, the lubricating property of metalworking oils based on mineral oils such as emulsion-based cutting oils and non-aqueous cutting oils are improved by adding an oiliness improver such as a fatty acid ester and a fatty acid or an extreme pressure additive containing an element such as sulfur, chlorine and phosphorus. However, the use of the extreme pressure additive containing chlorine has become difficult due to destruction of the ozonosphere, and the use of the extreme pressure additive containing phosphorus has become difficult due to the environmental problems such as the eutrophication caused by factory disposal. Although an excellent lubricating property can be obtained by using a polyether, it is difficult that the appearance of the product is made uniform due to poor compatibility of the polyether with hydrocarbon-based base oils such as mineral oils.
Among various metals, copper has the characteristic that excellent thermal conductivity and excellent workability are exhibited. Among the applications of copper-based metals, copper piping used for heat exchangers of air conditioners is one of applications regulated by the most rigorous quality standards. In general, copper tubes used for this piping are produced by drawing and shipped after cleaning, drying and annealing. In the drawing, the condition of the working is severe and, in general, it is necessary that an excellent lubricant satisfying viscosity characteristic and workability be used.
As the oil composition for metalworking and the lubricating oil composition, the following compositions have been disclosed: metalworking oil compositions containing oxygen-bearing compounds which are selected from alkylene oxide adducts of polyhydric alcohols having 3 to 6 hydroxyl groups and hydrocarbyl ethers of alkylene oxide adducts of polyhydric alcohols having 3 to 6 hydroxyl groups or oxygen-bearing compounds which are selected from specific polyalkylene glycols, hydrocarbyl ethers of specific polyalkylene glycols and dihydric alcohols having 2 to 8 carbon atoms (for example, Japanese Patent Application Laid-Open No. Heisei 10 (1998)-8080); lubricating oil compositions containing a polyester composition for lubricant containing a polyester having a viscosity of 3,000 to 25,000 cps and obtained by reacting a partial ester with a dibasic acid in an amount of 0.7 to 1.0 moles per 1 mole of the partial ester, wherein the partial ester is obtained by reacting a polyol having a functionality of 3 to 6 with a fatty acid having 12 to 22 carbon atoms in a manner such that the residual hydroxy group of the polyol shows a functionality of 2.0 to 2.5, (for example, Japanese Patent Application Laid-Open No. Heisei 8 (1996)-208814); metalworking oil compositions containing an additive which contains a reaction product of an epoxidized alkyl ester of a fatty acid and an amine compound (for example, Japanese Patent Application Laid-Open No. 2000-186292); and metalworking oils comprising a specific polyether having an HLB of 6.0 or smaller and a weight-average molecular weight of 500 to 30,000 (for example, Japanese Patent Application Laid-Open No. 2003-238978). However, these lubricating oil compositions for metalworking do not satisfy the requirements for the annealing property and the lubricating property simultaneously.
On the other hand, copper has the characteristic that excellent thermal conductivity and excellent workability are exhibited. Among the applications of copper-based metals, copper piping used for heat exchangers of air conditioners is one of applications regulated by the most rigorous quality standards. In general, copper tubes used for this piping are produced by drawing and shipped after cleaning, drying and annealing. In the drawing, the condition of the working is severe and, in general, it is necessary that an excellent satisfying viscosity chracteristic and workability be used (for example, Japanese Patent Application Laid-Open No. 2000-263125).
However, recently, a process without cleaning with an organic solvent is desired from the standpoint of the environment. Based on the efforts by manufacturers of lubricants, drawing oils for producing copper tubes using an easily thermally decomposable macromolecular substance such as polybutene as the base oil have been developed to replace oils using mineral oils as the base oil (for example, Japanese Patent Application Laid-Open Nos. Heisei 11 (1999)-193390, Heisei 11 (1999)-209781, Heisei 11 (1999)-349975, 2000-96073 and 2000-186291).
However, since the cleaning step of the drawing oil is omitted in the process for producing copper tubes, a great problem arises in that the color of copper tubes changes when a conventionally used strong sulfur-based extreme pressure additive is used in the production of the copper tubes. Another great problem is the amount of residual oil. The standard for the residual oil in Japan is as severe as 0.1 mg/m. The oil mainly used at present is prepared by adding a fatty acid ester-based additive and has a viscosity characteristic. When this oil is used, side reactions take place due to heating during the annealing, and it is difficult that the amount of the residual oil is decreased.